Battery booster with preconditioning and temperature compensation

ABSTRACT

A self-contained emergency battery charger for use in motor vehicles for charging a fully or partially discharged starter storage battery which delivers current to a starter motor of the vehicle. The batter charger contains a preconditioning circuit to preconditions a discharged battery before applying a full charging current from a charged second battery to the discharged battery. The battery charger also contains a temperature circuit which adjusts the time of charging whereby the time for providing power from the second battery is increased or decreased in relation to the second battery&#39;s temperature.

BACKGROUND OF THE INVENTION

[0001] This invention relates to battery charging devices, and inparticular to a self-contained emergency battery charger for use inmotor vehicles for charging a fully or partially discharged starterstorage battery which delivers current to a starter motor of thevehicle.

[0002] A motor vehicle storage battery frequently falls into a state ofdischarge such that it cannot deliver sufficient current to the startermotor. This is often due to lights or other accessories being accidentlyleft on. Also, defective vehicle charging systems can result in the sameproblem.

[0003] To start a vehicle whose storage battery has been partially orcompletely discharged requires either by-passing the electrical startingsystem entirely or supplying the electrical starting system with anadditional source of external electrical power. The former technique isgenerally accomplished by push-starting the vehicle and the lattertechnique by using either jumper cables connected to a fully chargedexternal power source in another vehicle, termed “jump starting”, or aconventional battery charger. Push starting requires assistance in theform of a push vehicle or human muscle power. Additionally, only carsfitted with standard transmissions can be push started. Jump startingrequires the aid of an additional vehicle. Further, cables must beavailable and must be externally connected, requiring the user to exitthe vehicle, and be exposed to the hazards of weather or of possiblebattery explosion and associated mishaps as a result of a misconnectionof the cables. The disadvantage of a conventional battery charger is theneed to be near a source of external power such as 120 volts alternatingcurrent.

[0004] To overcome these problems and the limitations of prior artattempts to solve the problem, such as being useful only for one or twobattery charges before the secondary battery source must be replaced, avery slow recharge cycle, a need for an external source of power, andinsufficient portability or lengthy charging/recharging times, assigneedeveloped a battery booster, subsequently patented as U.S. Pat. No.5,637,978, issued on Jun. 10, 1997, said patent being incorporatedherein by reference and hereinafter referred to as the '978 batterybooster.

[0005] Through extensive testing of lead acid batteries Applicants havelearned that a fully drained automotive (lead acid) battery will notaccept current and return it efficiently under certain conditions.Specifically, Applicants have found that when a lead acid battery(originally a nominal 12 volts) is discharged below 5 volts, the chargeacceptance is <40%. The original design parameters for the '978 batterybooster were to deliver 5 amps constantly from the time the chargingswitch is activated. During testing, limited success was achievedstarting vehicles. The 1978 battery booster, as originally designed wassuccessful in starting vehicles whose discharged batteries were ≧9.5volts. Further research verified that low current return occurred whenthe lead acid battery was <5 volts. A very high rate of current return(88% to 92%) occurred when the lead acid battery was >10.5 volts.

[0006] During their research, Applicants also found a variation in timerequired to recharge a lead acid battery. Applicants found that, withinoperating temperature limits, during a given time period, a warm batterywill provide more electrical power than cold battery. Therefore, undercolder conditions the time required to fully recharge a battery islonger. The original '978 battery booster had a simpleresistor/capacitor circuit that took a resistor of fixed value andcharged a capacitor of a fixed value giving a fixed time regardless oftemperature.

SUMMARY OF THE INVENTION

[0007] The present invention “preconditions” a discharged battery beforeapplying a full charging current from a charged second battery to thedischarged battery. The invention circuitry first checks the voltagelevel of the discharged battery. If the voltage level is at or below afirst predetermined level, a minimum charging current, which is lessthan half the value of a full charging current, is applied to thedischarged battery from the second battery. The minimum charging currentis applied to the discharged battery until the voltage of the dischargedbattery rises to a second predetermined level. After the voltage of thedischarged battery reaches the second predetermined level, the inventionapplies a full charging current to until the discharged battery is fullycharged.

[0008] In providing the charge to the discharged battery from thecharged second battery, the present invention adjusts the time ofcharging whereby the time for providing power from the second battery isincreased or decreased in relation to the second battery's temperature.

[0009] These together with other objects of the invention, along withvarious features of novelty which characterize the invention, arepointed out with particularity in the claims annexed hereto and forminga part of this disclosure. For a better understanding of the invention,its operating advantages and the specific objects attained by its uses,reference should be had to the accompanying drawings and descriptivematter in which there is illustrated a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of the invention.

[0011]FIG. 2 is a schematic circuit diagram of the prior art.

[0012]FIG. 3 illustrates the diagram of FIG. 2 modified according to thepresent invention.

[0013]FIG. 4 is a schematic circuit diagram according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention is an improvement in providing a charge toa discharged battery from a charged second battery as identified in the'978 patent. Specifically, the present invention adds a preconditioningstep to the charging process as well as temperature compensation.

[0015] The invention has a generally box-like, rectangularly shapedhousing 1, having a front 2, back 3, two sides 4, a top 5 and a bottom6. The housing front 2 has a panel 10 attached covering the entirehousing front 2. Visible horizontally across the panel 10 from the leftside 4 to the right side 4′ are an auxiliary power tap 11 which allowspower to be drawn from the invention power source 30, i.e., chargingbattery, for non-vehicle battery-charging purposes. Immediately to theright of the tap 11 is an opening 12 through which a power cord 16passes, said power cord 16 terminating in a male receptacle 17 adaptedfor insertion into a vehicle's cigarette lighter receptacle 27. The malereceptacle 17 has a positive lead 18 terminating centrally along itscentral longitudinal axis and a cylindrical housing 19 connected to theinvention common ground 38. Immediately to the right of said opening 12is a first switch 13 which is a three-way switch. The switch 13 providesa “Charge” setting 13A, an “Off” setting 13B and a “Recharge” setting13C. To the right of the switch 13 are two light indicators 14, 15. Thelight indicator 14 immediately to the right of the switch 13 is yellowand indicates various vehicle storage battery 20 charging modes. Thenext light indicator 15 is green and indicates various inventioncharging, recharging and test modes.

[0016]FIG. 2 illustrates the circuit diagram of the '978 patent.Referring to FIG. 2, there is shown a vehicle storage battery 20. Avehicle storage battery is typically a 12 volt, 40 Ampere-Hour, leadacid battery. A vehicle storage battery 20 and vehicle cigarette lighter25 electrical circuit is shown. The lighter 25 is formed of a femalereceptacle 27 terminating centrally along its central longitudinal axisin a positive lead 26. There is a fuse 23 between the positive terminal21 of the vehicle storage battery 20 and the lighter positive lead 26.The lighter receptacle 27 is electrically connected to the batterynegative terminal 26.

[0017] The invention has a charging battery 30. The nominal voltageoutput from the charging battery 30 is represented by the symbol Vc. Thecharging battery 30 in this embodiment of the invention is a 12 volt, 7Ampere-Hour, sealed, lead acid battery. This type of battery is rated at12 volt nominal output. The charging battery 30 has a positive terminal31 and a negative terminal 32.

[0018] An optional auxiliary circuit is formed with the charging battery30 to the auxiliary power tap 11. The tap 11 is comprised of a femalereceptacle 35 terminating centrally along its central longitudinal axisin a positive lead 36. The tap positive lead 36 is electricallyconnected by means of electrical line 37 to the charging batterypositive terminal 31. The tap receptacle 35 is electrically connected toa common ground 38 terminating in the charging battery negative terminal32. This embodiment of the invention contains a positive temperaturecoefficient resistor, P1, between the charging battery negative terminal32 and the common ground 38. The resistor, P1, is variable andnon-linear. P1 has a low resistance value at relative low temperatures,but has substantially higher resistance at high temperatures. P1 acts asa current limiting fuse. P1 will exhibit low resistance characteristicsat less that 6 amps and very high resistance at greater than 6 amps.

[0019] Also shown is a depiction of the three-way switch 13 mentionedabove. The switch 13 may be termed a first switching means and isadapted to electrically connect the battery positive terminal 31 to oneof three nodes 13A, 13B or 13C. The switch 13 provides a “Charge”setting when the battery positive terminal 31 is connected to node 13A;an “Off” setting when connected to node 13B; and a “Recharge” settingwhen connected to node 13C. The switch 13 is shown in its “Charge”setting 13A. The “Charge” setting establishes a circuit whereby thecharging battery 30 and other invention circuitry charge the vehiclestorage battery 20 through the cigarette lighter 25. The “Recharge”setting establishes a circuit whereby the invention charging battery 30is recharged from the vehicle storage battery 20 through the cigarettelighter 25.

[0020] The “Charge” circuit established by the switch 13 places acapacitor C2 in parallel to the charging battery 30 wherein thecapacitor C2 positive terminal 61 is electrically connected to theswitch node 13A. A resistance network comprised of two resistors R6, R8,in series, is also electrically connected in parallel with the capacitorC2. An RC (resistance-capacitance) network comprised of a resistor R11and capacitor C3, in series, is also electrically connected in parallelwith the resistance network R6, R8. An inductance L1 and diode D1 areelectrically connected in series with the charging battery positiveterminal 31 wherein the inductance L1 input terminal 40 is electricallyconnected to the capacitor C2 positive terminal 61, the resistancenetwork R6, R8 positive node 60, and the RC network R11, C3 positivenode 62. The inductance L1 output terminal 41 is connected to the diodeD1 positive terminal 42. The diode D1 negative terminal 43 is connectedto the positive lead 18 of the power cord male receptacle 17. A secondswitch U1, having a primary terminal 55 and two secondary terminals, one56 of said secondary terminals being positive and the other 57 beingnegative, said secondary terminals 56, 57 being adapted to jointlyconnect to said primary terminal 55 or being jointly disconnected fromsaid primary terminal 55, said positive secondary terminal 56 beingconnected to said inductance L1 output terminal 41 and said negativesecondary terminal 57 being connected to said common ground 38, therebyinterconnecting the inductance L1 output terminal 41 to ground 38 whenthe switch U1 is closed. A diode D3 interconnects the positive terminal52 of the switch U1 with the junction 73 of R11 and C3. A U1 switchcontrol 50 interconnects the inductance L1 input terminal 40 to ground38. The switch control 50 is electrically connected to the switch U1 andalso is connected to a resistance network comprised of two resistors R1,R2, in series. The resistance network R1, R2 interconnects the diode D1negative terminal 43 to ground 38. The switch control 50 is connected tothe junction 51 of R1 and R2. A capacitor C1 is connected in parallel tothe resistance network R1, R2 wherein the capacitor C1 positive terminal45 is electrically connected to the resistance network R1, R2 positivenode 63. The diode D1 negative terminal 43, resistance network R1, R2positive node 63, and capacitor C1 positive terminal 45 are electricallyconnected to the positive lead 18 of the power cord male receptacle 17.

[0021] To charge the vehicle battery the switch 13 is set to “Charge”mode. The power cord male receptacle 17 is inserted into the cigarettelighter 25 thereby establishing an electrical connection among the C1positive terminal 45, the diode D1 negative terminal 43 and theresistance network R1, R2 positive node 63, and the vehicle batterypositive terminal 21, and thereby establishing an electrical connectionbetween the vehicle battery negative terminal 22 and the inventioncommon ground 38. The C1 negative terminal 46 is also attached to thecommon ground 38. In the “Charge” mode the invention must be capable ofstepping up the voltage from the loaded terminal voltage Vc of thecharging battery 30 to the terminal voltage required to charge thevehicle storage battery 20, i.e., from approximately 12 volts toapproximately 14 volts. In the present invention this is done by meansof a “boost converter” which is that portion of the circuit comprised ofthe elements L1 (inductance), D1 (diode), and U1 (switch). The switch U1is controlled by a switch control unit 50. The switch control unit 50 isself-oscillating with a switching rate based upon output voltagefeedback across the resistance network R1 and R2. The voltage betweenthe inductance L1 positive terminal 40 and ground 38 supplies power tothe switch control unit 50 circuitry. In the switch “Charge” setting, anelectrical connection is made across terminal 13A thereby electricallyconnecting an input filter capacitance, C2, from the charging batterypositive terminal 31 to the common ground 38. C2 provides a filteringfunction and a low impedance input to U1. C1 provides a load for thebooster converter to discharge into in case the fuse 23 is blown or someother similar situation arises. The Charging setting also connects thecharging battery positive terminal 31 in electrical series connectionwith the input terminal 40 of the inductance L1. In the Charging mode,when the switch U1 closes, the inductance L1 is in series with thecharging battery 30. Current in the inductance L1 increases slowlyrising to 5 amps. Because of the nature of an inductance, when theswitch U1 opens, current will still flow in L1 and the voltage across L1will adjust to maintain current flow. Since the voltage at the L1 inputterminal 40 must equal Vc, there will be a polarity change wherein thevoltage at the L1 output terminal 41 will become greater than Vc at theL1 input terminal 40 thereby maintaining current flow in L1. With thepower cord male receptacle 17 connected to the cigarette lighter 25, thepositive terminal 21 in the vehicle storage battery 20 will feel thegreater voltage at the L1 output terminal 41. The effect of this greatervoltage will cause the L1 5 amp current to flow into the vehicle storagebattery 20. The inductance L1 in effect acts as a current fly wheel. D1prevents the vehicle storage battery 20 from discharging back into L1.The switch U1 will then close again and the process will repeat.

[0022] The “Recharge” circuit established by the switch node 13Cinterconnects a positive temperature coefficient resistor, P2, with thecharging battery positive terminal 31 and the vehicle battery positiveterminal 21. By connecting the power cord male receptacle 17 with thevehicle cigarette lighter 25, an electrical connection between thevehicle battery negative terminal 22 and the invention common ground 38is established. Like P1, the resistor, P2, is variable and non-linear.P2 has a low resistance value at relative low temperatures, but hassubstantially higher resistance at high temperatures. Initially, theresistance of P2 rises very slowly as temperature rises. After thetemperature reaches a designated value, the resistance of P2 risesexponentially. P2 is also current limiting and acts as a self-repairingfuse. Unlike prior art devices, P2 allows the charging battery 30 torecharge without exceeding the safe recharging current, i.e.,approximately 2 amps. The Recharge circuit is basic and permits a simpleand efficient method of recharging the invention charging battery 30after use.

[0023] The light indicators 14, 15 indicate to the user what ishappening and in this embodiment of the invention are light emittingdiodes (LEDs). A resistance network comprised of two resistors R9, R10,in series, is electrically connected between the switch node 13C andground 38. An LED control unit 70 is connected to the junction 71 of R9and R10. The LED control unit 70 is also connected to the junction 72 ofR6 and R8, and also to the junction 73 of R11 and C3. The positiveterminal 74 of the yellow LED 14 is electrically connected to the switchnode 13A and the positive terminal 76 of the green LED 15 iselectrically connected to the switch node 13C. The negative terminal 75of the yellow LED 14 and the negative terminal 77 of the green LED 15are both connected to the LED control unit 70. In operation, the greenLED 15 lights when the switch 13 is in the “Charge” position at switchnode 13A and Vc is below 9.5 volts thereby indicating that no charge isleft in the charging battery 30. Power to light the green LED 15 andoperate the LED control unit 70 comes from the vehicle storage battery20. The green LED 15 also lights when the switch 13 is connected to the“Recharge” position 13C and Vc is above 12.5 volts thereby indicatingthat the charging battery 30 is fully charged. Voltage feedback signalsfor these two conditions are provided by the resistance networkscomprised of R6 and R8, and R9 and R10, respectively. The yellow LED 14operates as follows. If the voltage across C3 is less than a designatedreference voltage, the yellow LED 14 will be turned on. If the voltageacross C3 is greater than a designated reference voltage, the yellow LED14 will be turned off. When switch U1 closes, C3 is discharged via D3.When U1 opens, C3 slowly recharges via R11. If U1 is being switched athigh frequency then the average charging voltage on C3 will be low andusually below a reference voltage, resulting in the yellow LED 14 beingbrightly illuminated thereby indicating that current is beingtransferred from the charging battery 30 to the vehicle storage battery20. If vehicle battery 20 is not connected via the cigarette lighter 25and plug 17, the voltage across C1 will rise and the switch U1 willoperate at a low frequency. This results in a greater charging voltageacross C3, usually greater than the reference voltage, and consequentlyan apparently dimmer yellow LED 14 because of the greater amount of timethe LED 14 is turned off.

[0024] The performance of the invention on a particular vehicle may becalculated as follows. To determine the energy transfer to the “dead”vehicle storage battery 20, multiply the time (in hours) by the chargecurrent (typically 5 Amperes) and factor the “charge-discharge”efficiency of the vehicle storage battery 20 (assume 50%). Since thebattery charger will be a “constant current” device, the energytransferred to the vehicle storage battery 20 will be linear with time.On the assumption that it will take about 0.56 Ampere-Hours to start atypical, but cold, functioning vehicle engine (200 Amperes×10seconds×3600 seconds/hour), it will take about 15 minutes to transferenough energy to start the vehicle. If the vehicle storage battery 20 isnot discharged as much, less charging time will be required. The aboveperformance figures are stated at 32° F. (0° C.).

[0025] Referring to FIGS. 3 and 4, the present embodiment of theinvention, provides a 2 ohm, 10 watt, block resistor R-7 in parallelwith a power MOSFET on the negative side of the unit. The block resistorhas a resistance in the range of 1 to 4 ohms, and a watt rating of from8 to 12 watts. When the unit is turned on, the preconditioning stepprevents excessive current levels when the voltage differential betweenthe vehicle battery and the charging battery is high. This step providespreconditioning to the depleted battery. The resistor limits thecharging current to 7 amps. The preconditioning charge of 7 amps ismaintained until the discharged battery voltage reaches 10.5 volts orwhen the voltage differential across the resistor is less than 2 volts.This generally takes from 30 to 35 seconds. When this point is reached,an operational amplifier is activated turning on the FET that completesthe negative path. In this embodiment of the invention this is the mostefficient charge point. At this point of activation a DC-to-DC “up”converter is engaged to boost the DC level of the charging battery to15-17 amps. The invention will run in the fully charging mode from 10 to15 minutes. The invention uses a current mode PMW controller device thatprovides cycle-by-cycle current limitation that prevents over-currentconditions from occurring. A timer is also incorporated into theinvention that activates the second green light at a predetermined time.

[0026] The original circuitry in the '978 patent (see FIG. 2) had asimple resistor/capacitor circuit that took a resistor of fixed valueand a charge capacitor of fixed value giving a fixed time regardless oftemperature. For temperature control, a thermistor th-1 is placed inseries with the resistor R-11 to vary the time it takes to charge thecapacitor depending on the unit's temperature. In this embodiment of theinvention the thermistor is a negative type where a decrease intemperature results in an increase in resistance resulting in longertime to charge the capacitor. The temperature of both the dischargedbattery and the second battery is dependent upon the ambient temperatureand time of either battery to reach that temperature if, before use,either is at a temperature different than the ambient temperature. Forexample is the situation where the second battery is brought to a coldgarage holding the vehicle with the discharged battery.

[0027] It is understood that the above-described embodiment is merelyillustrative of the application. Other embodiments may be readilydevised by those skilled in the art which will embody the principles ofthe invention and fall within the spirit and scope thereof.

We claim:
 1. A self-contained emergency battery booster for charging,through a vehicle's cigarette lighter receptacle, a fully or partiallydischarged vehicle storage battery which delivers current to a startermotor of the vehicle, comprising: a housing having a rectangular shapewith a front, back, two sides, a top and a bottom, said housing havingan auxiliary power tap adapted to draw power from a charging battery fornon-vehicle battery charging purposes, said housing having an openingthrough which a power cord passes, said auxiliary power tap forming anauxiliary circuit formed with the charging battery, said tap beingcomprised of a female receptacle terminating centrally along its centrallongitudinal axis in a positive lead, said positive lead beingelectrically connected by means of an electrical line to a chargingbattery positive terminal, said receptacle being electrically connectedto a common ground connected to a charging battery negative terminal,said auxiliary power tap auxiliary circuit having a positive temperaturecoefficient resistor between the charging battery negative terminal andthe common ground; said charging battery within said housing providing acharging battery output, said charging battery having a nominal terminalvoltage equal to or less than the nominal voltage of the vehicle'sstorage battery, said charging battery having said positive terminal andsaid negative terminal; first switching means within said housingconnected to said charging battery positive terminal, said firstswitching means being comprised of a three-way switch adapted toelectrically connect the charging battery positive terminal to one ofthree nodes, a charge node, an OFF node, and a recharge circuit, saidconnection to said charge node establishing a circuit whereby thecharging battery and a boost converter circuit charge the vehiclestorage battery through said cigarette lighter receptacle, saidconnection to said recharge node establishing a circuit whereby thecharging battery is recharged from said vehicle storage battery throughsaid cigarette lighter receptacle, and said connection to said OFF nodeelectrically opens said charging battery positive terminal; said boostconverter circuit within said housing connected to said first switchingmeans and adapted to derive energy from said charging battery whereinsaid boost converter circuit provides an additional 2 to 3 volts outputto said charging battery output; means for connecting said chargingbattery output and said booster circuit output to said vehicle storagebattery, said means comprising said power cord terminating in a malereceptacle adapted for insertion into said vehicle's cigarette lighterreceptacle, said male receptacle having a cylindrical housingelectrically connected to said charging negative terminal therebyforming said common ground and a positive lead formed centrally along acentral longitudinal axis and connected to said boost converted circuit;indicator means mounted on said housing adapted to indicate the chargingstatus of the charging battery and the vehicle storage battery; whereinsaid charge node circuit is comprised of: a second capacitorelectrically in parallel to the charging battery wherein a positiveterminal of said second capacitor is electrically connected to saidswitch charge node and a negative terminal of said second capacitor isconnected to said common ground; a first resistance network comprised oftwo resistors in series electrically connected in parallel with saidsecond capacitor; a resistance-capacitance network comprised of aresistor and third capacitor in series, said resistance-capacitancenetwork being electrically connected in parallel with said firstresistance network; said booster converter circuit comprised of: aninductance having an input terminal and an output terminal, said inputterminal being electrically connected to the second capacitor positiveterminal, a first resistance network positive node, and aresistance-capacitance positive node; a first diode having a positiveterminal and a negative terminal, said positive terminal being connectedin series with said inductance negative terminal, said first diodenegative terminal being connected to the positive lead of the power cordmale receptacle; and a second switch having a primary terminal and twosecondary terminals, one of said secondary terminals being positive andthe other being negative, said secondary terminals being adapted tojointly connect to said primary terminal or being jointly disconnectedfrom said primary terminal, said positive secondary terminal beingconnected to said inductance output terminal and said negative secondaryterminal being connected to said common ground; and a second switchcontrol means adapted to operate said second switch; a second resistancenetwork comprised of two resistors in series, said second resistancenetwork interconnecting said first diode negative terminal to saidcommon ground; and a first capacitor, having a positive terminal and anegative terminal, connected in parallel to the second resistancenetwork wherein said first capacitor positive terminal is electricallyconnected to a second resistance network positive node, and said firstcapacitor negative terminal is attached to common ground; wherein saidfirst diode negative terminal, said second resistance network positivenode, and said first capacitor positive terminal are electricallyconnected to the positive lead of the power cord male receptacle;wherein said power cord male receptacle is inserted into said cigarettelighter receptacle thereby establishing an electrical connection amongthe first capacitor positive terminal, the first diode negative terminaland a second resistance network positive node, and the vehicle batterypositive terminal, and thereby establishing an electrical connectionbetween the vehicle battery negative terminal and said common ground; apreconditioning circuit comprised of a block resistor in parallel with apower MOSFET connected between a charging battery negative terminalcircuit and the common ground.
 2. A battery booster as recited in claim1 , further comprising: a temperature circuit comprised of a thermistorplaced in series with the resistance-capacitance network resistor.
 3. Abattery booster as recited in claim 2 , wherein: said block resistor hasa resistance in the range of 1 to 4 ohms, and a watt rating of from 8 to12 watts.
 4. A battery booster as recited in claim 3 , wherein: saidthermistor is adapted to increase in resistance when ambient temperaturedecreases.